We know that,
if two angles are complementary, then their sum is $$90^o$$.
Given, the angle is $$ (x+5)^o$$.
Then, the complement of $$ (x+5)^o$$ is:
$$=90^{0}-(x+5)^{0}=90^o-x-5^o=85^o-x=(85-x)^o$$.